The present invention is related generally to computing system network configurations, and more particularly to a network configuration that is tolerant of faults that may occur.
Fault tolerant computing systems have long been known. In environments in which high availability of computing tasks are desired, computing systems have included various fault tolerant designs such as redundant parts, elements or modules, data checking and correcting schemes, and the like. An example of a fault tolerant computing system may be found in U.S. Pat. No. 4,228,496, which teaches a multi-processing system having fault tolerant capability for example in the form of redundant facilities to limit single points of failure.
One use of such high availability computing systems is as a "server" in various network configurations, such as, for example, local area network (LAN) designs. As a server, the computing system stores and maintains the various resources (e.g., application programs, data, etc.) used by the stations (e.g., personal computer (PC) systems) connected to the network. It was soon realized, however, that even though the server unit may be structured to provide high availability, the network itself limited that availability in that the network contained single points of failure. For example, cables can break, or inadvertently be removed, eliminating a communication path of the network and, more likely than not, isolating one or more stations from the server.
Solutions to this problem have included providing fully redundant networks. However, this solution has required the application programs to be extensively rewritten, thereby effectively eliminating the use of off-the-shelf application programs.
Thus, it is apparent that there is a need for extending the fault tolerant high availability provided by multi-processor systems such as that of the aforementioned U.S. Pat. No. 4,228,496 to the network with which it may be used and connected. This extension of fault tolerance should be done in such a way so that applications run on workstations or the network need no, or little, revision or modification.